Wow so many replies were to start
No i don't work for british gas but used to work for a similar "good co !!"
was cr 15 years ago but not now job move for sanity
no i was not checking the inlet as only 1 tp on the gas valve
and because on this type of boiler the gas valve was held...
I have just moved in to a house with one of these boilers and all seems to be working fine
on closer looking however the isolating valve is shut half way down ! when i turn it on fully the main burner is way to high and reads too high on the water gauge
pardon my ignorance but i can not see...